Garden LED Lighting on Mains power


Old 08-30-08, 11:05 AM
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Garden LED Lighting on Mains power


I have some LED garden lights around my decking outside and they currently run from a solar panel which charges during the day and powers the lights at night. However, with the british summer not providing any sun lately the lights don't always come on at night!

I want to power the lights from the mains with a weather proof transformer but don't know what voltage I should be looking for. The 2 rechargable batteries in the solar panel are AA 1.2v 1000mAh Ni-MH and these run 4 led lights. I have 2 sets and want to run both from the one transformer. Will a 12v transformer do this or will it blow the LED's?

Thanks in advance
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Old 08-30-08, 02:12 PM
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You can be sure of it. Blowing your LEDS that is. Perhaps someone will come along with a solution. "Frenchie" where are ya? Your ol neighbor has a question.
Old 08-30-08, 05:36 PM
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More likely as not the two AA batteries are wired in series to produce 2.4 volts to the LEDs. You would need a power supply that would output slightly more than 2.4 volts direct current at no more than about 100 to 200 mA to prevent damaging the batteries.

Or, if you removed the batteries completely then the power supply could be wired directly to the LEDs with a series resistor to limit the current flow to about 30 mAs per LED. It is quite possible that the necessary current limiting circuit already exists in the circuitry of the lamps and you could simply wire the 2.4 volts D.C. to where the batteries are presently connected. Polarity IS important.
Old 08-30-08, 09:34 PM
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12V will most likely blow up the LEDs or, worse, be dangerous to overheating as the LEDs will draw current way beyond their specs. 2AA @ 1.2v would imply a 2.4V source. HOWEVER when it comes to LEDs it is not simply a matter of voltage. LEDs are not simply resistors where current is proportional to voltage. LEDs need a resistor in series to protect them from overcurrent. Otherwise even a small overvoltage will cause excessive current. Now since your LEDs are powered by batteries the circuit may already have a resistor in series but that is hard to tell.

Bottom line, keeping safety in mind, I would not attempt hooking the LEDs up to a source capable of high current (i.e. a transformer, even a 2.4V one) without measuring how much current they draw under these circmstnces and, equally important, how the current varies at different voltages. You would no want a situation where the 2.4V transformer occasinally puts out 3V and creates a dangerous overcurrent.
Old 08-31-08, 01:04 AM
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Myself ,.. I don't have full experance with the LED lumianire something like you describing However., I know some of the solar LED luminaire do have a aux power jack so you can hook up the " house " power something like one of the low voltage circuits.

I am pretty sure one manufacter or two do have a low voltage LED outdoor luminaire.

On other hand Both Furd and ThomasE did pretty good expaining about the LED fuction and that part you have to becarefull to prevent from getting overcurrent on them they are very senstive.

Old 08-31-08, 04:26 AM
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Thanks for the responses guys. I guess a transformer is not an option then. Unfortunately the solar unit with the batteries in does not have an AUX connection for an external power supply. I suppose I could charge the batteries with a seperate charger and replace them when we want lighting! Bit of a pain in the neck, wish I went for the lights which run off mains power in the first place

Thanks again

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